Recovery of propargyl alcohol



July 9, 1963 R. R. MaCGREGOR 3,097,147

RECOVERY OF PROPARGYL ALCOHOL Filed March 16, 1961 2 Sheets-Sheet 2 FIGZ.

PROPARGYL ALCOHOL RECOVERED IN DISTILLATE,WEIGHT PERCENT 0 IO 20 30 40 50 WATER IN COLUMN FEED, WEIGHT PERCENT FIGB.

PROPARGYL ALCOHOL IN OVERHEAD, WEIGHT PERCENT O I0 2O 30 40 50 WATER IN COLUMN FEED,WEIGHT PERCENT INVENTOR ROB R. MAC GREGOR (3M f ATTORNE 3,097,147 RECOVERY F PROPARGYL ALCHOL Rob R. MacGregor, Hopewell, Va., assigner to Allied Chemical Corporation, New York, NSY., a corporation of New York Filed Mar. 16, 1961, Ser. No. 96,179 7 Claims. (Cl. 202-42) This invention relates to a process for recovering propargyl alcohol. It relates more particularly to a process whereby propargyl alcohol contained in solution in N- methyl-Z-pyrrolidone or other N-alkyl-Z-pyrrolidone having 2 to 8 N-alkyl carbon atoms can be eifectively recovered as la substantially pure product in a simple manner.

An object of the present invention is to provide a process for the recovery of propargyl alcohol fom mixtures thereof with N-alkyl-Z-pyrrolidones containing l to 8 carbon atoms in the N-alkyl radical.

Another object of the present invention is to provide a process for the effective recovery of propargyl alcohol in a simple manner from solutions thereof in N-methyl-Z- pyrrolidone.

An additional object of the present invention is to provide a process for the separation and recovery of propargyl alcohol from solutions thereof in N-methyl-Z-pyrrolidone or other N-alkyl-Z-pyrrolidone containing 2-8 N-alkyl carbon atoms by a simple distillation procedure.

A further object of the present invention is to provide a method for the recovery and purification of propargyl alcohol from an laqueous solution of propargyl alcohol in N-rnethyl-Z-pyrrolidone containing butynediol and formaldehyde, and especially from such a solution resulting from the ethynylation of formaldehyde by reaction with acetylene in the presence of a copper acetylide catalyst in aqueous N-methyl-2-pyrrolidone as reaction medium.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

Propargyl alcohol is an unsaturated alcohol having the formula HCEC-CH2OH Acetylene Formaldehyde (Copper Acet- Propargyl lide Alcohol Y Catalyst) Propargyl Formal- CuCg Butynediol Alcohol dehyde An improved process for the synthesis of propargyl alcohol from acetylene and formaldehyde is disclosed in my joint application with William P. Moore, Serial No. 847,223, iiled October 19, 1959. According to said irnproved process, a markedly high production rate of propargyl alcohol and a favorable propargyl alcohol: butynediol ratio is obtained at relatively low operating pressures by carrying out the reaction of acetylene with formaldehyde in the liquid phase in admixture with an N-alkyl-2-pyrrolidone and water, the concentration of Water preferably being 14% to 20% by weight and the pyrrolidone having l to 8 N-alkyl carbon atoms. The reaction mixtures resulting from such a process contain 3,097,147 a@ Patented July 9s 1953 Component- Weight percent Propargyl alcohol 8.82 Butynediol 2.97 Formaldehyde 5.82 Water 17.1 N-methyl-Z-pyrrolidone 65.1 Cuprene 0.14

The recovery of propargyl alcohol from its mixtures with N-alkyl-Z-pyrrolidones containing l to 8 carbon atoms in the N-alkyl radical, and especially from mixtures of the above type, presents a number of difficulties particularly in connection with the obtainment of a purified product.

lf it is attempted to recover the propargyl alcohol by distillation, the results are very unsatisfactory owing to the fact that the N-alkyl pyrrolidone prevents the distillation of a water-propargyl alcohol azeotrope. Moreover, if it is attempted to dehydrate the mixture by azeotropic distillation with the aid of an added liquid such as benzene, only the water is removed, leaving an anhydrous solution of propargyl `alcohol in the N-alkyl-pyrrolidone from which the propargyl alcohol cannot be readily separated.

Extractive methods of recovering the propargyl alcohol are also inoperative because the usual extractants (for example, ethyl acetate) are miscible with the other components.

According to the present invention, it has been found that high recoveries of propargyl alcohol from mixtures thereof with N-alkyl-2-pyrrolidones of the above class can be obtained by distillation of said mixtures, provided Water is present in the mixture subjected to distillation in amounts of at least '25% and preferably at least 30% by weight. I have discovered that recoveries of propargyl alcohol in the overhead distillate exceeding 97% by weight can be obtained when the mixture of propargyl alcohol and N-alkyl-pyrrolidone subjected to distillation contains at least 30% of water by weight; whereas recoveries of less than 43% by weight of propargyl alcohol are obtained when said mixture contains less than 25% of Water by Weight.

While I do not wish to be limited -to any theoretical considerations, it is postulated that a weak chemical bond between the N-alkyl-pyrrolidone and propargyl alcohol causes a negative deviation from Raoults law which makes the separation of the components by distillation diicult, if not impossible. The addition of water in amounts giving ka concentration of -at least 25% and preferably at least 30%, by weight, serves to counteract this eifect and permits distillation of a water-propargyl alcohol azeotrope from which the propargyl alcohol can be readily recovered in lanhydrous fonm and further purified in the known manner; for example, by removal of water by azeotropic distillation with a suitable liquid (e.g., isopropyl ether, cyclohexane, ethyl propyl ether or benzene), followed by vacuum distillation of the propargyl alcohol.

In order to avoid unnecessary dilution of the propargyl alcohol recovered as overhead distillate in the initial distillation, the amount of water added to the mixture subjected to distillation is preferably kept within reasonable limits. Thus, the concentration of water in the mixture generally does not exceed 45% by weight. By employing a concentration of water ranging from 30% to 35% by weight, substantially complete recovery of the propargyl alcohol can be obtained in the form of an aqueous distillate containing 14% or more by Weight of propargyl alcohol.

In the drawings, FIG. 1 is a diagrammatic ow diagram showin-g a preferred process for carrying out the recovery and purification :of propargyl alcohol contained in a mixture of the type referred to above.

FIG. 2 is a curve showing the effect of the concentration of water in the mixture subjected to distillation upon the recovery of propargyl alcohol in the overhead distillate.

FIG. 3 is a curve showing the effect of the concentration -of water in the mixture subjected to distillation upon the concentration of propargyl alcohol in the overhead distillate.

F or purposes of illustration, the mechanics of the process of this invention will be described in detail in connection with the recovery of propar-gyl alcohol from an aqueous mixture of propargyl alcohol and N-methyl-2- pyrrolidone containing by-product butynediol and unreacted formaldehyde and resulting from the ethynylation of formaldehyde by reaction with acetylene in the presence of a copper acetylide catalyst in aqueous N-methyl-2-pyrrolidone as reaction medium.

'I'he invention is not limited thereto, since other mixtures of propargyl alcohol and N-methyl-Z-pyrrolidone and mixtures produced in other ways, as Well as mixtures of propargyl alcohol with other N-alkyl-Z-pyrrolidones containing 1 to 8 carbon atoms in the N-alkyl radical, may be treated in similar manner to recover the propargyl alcohol.

A process for recovering propargyl alcohol, in accordance with the present invention, from a mixture of the type referred to labove is diagrammatically illustrated in FIG. 1 of the drawings. -In accordance therewith, an aqueous liquid solution of about 1 part of propargyl alcohol in about 7 parts of N-met-hyl-Z-pyrrolidone and about 2 parts of water, and containing about 0.3 part of by-product butyne-2diol-1,4 .and about `0.6 part of formaldehyde is fed in carefully controlled amounts from storage tank 1 simultaneously with a carefully controlled feed of water from storage tank 2 to feed line 3, so as to form a solution containing .about 30% of water. (All parts and percentages are by weight, unless otherwise stated.) This carefully controlled aqueous solution is passed through feed line 3L to a crude distillation column 4 operated at atmospheric pressure. With the column feed containing about 30% of water, all of the propargyl alcohol is taken off las overhead distillate along with water and unreacted formaldehyde, `and the N-methyl-Z-pyrroliwater and impurities, is removed via line 7. When it is done and by-product butynediol remain in the bottoms.

The overhead distillate is fed through line 5l to a continuous propargyl alcohol-water vacuum distillation columu 6 operated at 20 mm. Hg pressure, from which laqueous propargyl alcohol is removed as overhead distillate and led, by line 8, to a propargyl alcohol dehydration column 10. Water is removed by azeotropic distillation in column 10 in the form of a water-isopropyl ether azeotrope which passes overhead through line 11 and is separated in decanter 12, a part `of the water being returned as required for reuse through line 14 to Water storage 2 and the excess being discharged through line 32. Isopropyl ether is returned to the column through line 13 and additional isopropyl ether is supplied as makeup to the decanter from storage 30 through line 31.

Aqueous formaldehyde is removed from the bottom of column 6 through line 9. It can be returned t0 the desired to recover the butynediol and the N-methyl pyrrolidone separately, the cut is subjected to vacuum distillation in a column A19, operated at 40 mm. Hg pressure, wherein the N-methyl pyrrolidone is removed overhead as vapor through lines 20 and 24 and condensed in condenser 37.

The bottom cut of impure butynediol obtained in column :19 is passed via line 21 into a vacuum distillation column 22 operated at 10 mm. Hg pressure from which residual N-anethyl pyrrolidone is removed as overhead Vapor through line 23 and passed to condenser 37 through line 24.

The bottom cut of butynediol is removed from column 22 through l-ine 25'.

The curves in FIGS. 2 and 3, showing the effect of various concentrations of water in the aqueous solutions of propargyl alcohol in N-methyl-Z-pyrrolidone subjected to distillation, are based on data obtained by subjecting an aqueous `solution of .propiargyll alcohol in N-methyl-2- pyrrolidone, containing about 0.3 part of butyne-2-diol- 1,4, about 0.6 part of formaldehyde, per part of propargyl alcohol, and various amounts of water, to distillation at atmospheric pressure in a packed column 12 feet long, having :an inside diameter of 4 inches, and packed with 0.5 inch ring packing material. The column was operated Wit-h 9 ft. as a stripping section and 3 Ift. as a rectifying section, the reflux ratio being 1:1. The feed solution, which was introduced at the junction of said sections, contained 5.1-6.5% of propargyl alcohol and was fed at the rate of 3050 to 3470 gum/hr. r[The overhead temperature was l06-1f0-8 C. The pot temperature was 167 174 C.

FIG. 2 shows rthe curve obtained by plotting the per cent by Weight of propargyl alcohol recovered in the overhead distillate vs. percent by Weight of Water in the solution fed to the column.

PIG. 3 shows the curve obtained by plotting the percent -by Weight of propargyl alcohol contained in .the overhead distillate vs. percent by weight of water in the solution fed tot the column.

As is evident from FIGS. 2 :and 3, the percentage of propargyl alcohol recovered in the distillate rises rapidly t-o nearly y% when the water concentration reaches about 30%, and lthe concentration of propargyl alcohol in the distillate reaches a maximum between a water concentration of 30% and 35% in the solution yfed to the column.

The invention will be illustrated by .the following spevciiic example, but it is to be understood that it is not limited to the details thereof and that changes may be made 'without departing from the scope `of the invention. The temperatures are in degrees icentigrade and the parts and percentages are by Weight.

Example A liquid ethynylation product resulting from the reaction Kof acetylene with a mixture of formaldehyde and aqueous N-methyl-Z-pyrrolidone containing about 63% of methylpyrrolidone, about 18% of water, and about 5% of a suspension of 20% copper acetyliide on silica catalyst, all by Weight, at a temperature of C. and p.s.i.g. pressure, and having fthe composition set out in column 2, was mixed with water recycled from decanter 12 to give a feed to distillation column 4 having the following composition:

The column was operated at atmospheric pressure, a head temperature of 106 to 109, :and la bottom temperature of 167 to 174. The distillation at l06109 had the following composition:

Component-, Percent Propiargyl alcohol 17.59 Formaldehyde 112.1118 Water 69.86 Isopropyl ether- 0.37

The bottom cut at 167 had the following composition:

Componente- Percent N-methyl-2-pyrroli'done 91.41 Butynediol 4,17 Propargyl alcohol 0.61 Formaldehyde 0.16 Water 3.45 Cuprene 0.20

The distillate was fed to the propargyl alcohol-water distillation column 6, operated at 20 nun. Hg absolute pressure with Aa pot temperature or 13 6-42. An overhead stream was removed with the following composition:

Component- Percent Propargyl alcohol 27.23 Formaldehyde 0.72 Water 71.48 Other 0.57

The bottom cut contained about 361% formaldehyde. If desired, it can be concentrated to a 50% aqueous solution by 'distillation and returned -to the synthesis system for reuse.

The overhead from column 6 was -fed to the propargyl alcohol dehydration column where the water was removed as a water-isopropyl ether fazeotrope at 62 at atmospheric pressure. isopropyl ether was continuously decanted from the water and returned to the stillhead. A portion of the decanted waiter was returned to the water feed 2 and the remainder was discarded. Irt was necessary to add 0.03 lb. isopropyl ether/ lb. proplargyl alcohol recovered to make up for bleed losses.

The discolored pnopargyl alcohol discharged from the dehydration column 10 `through line 15 had the following composition:

Component- Percent Propargyl alcohol 96.0 Water 0.3 Formaldehyde 0.3 Other 3.4

Component- Percent Pnopargyl alcohol 99.50 Water 0.44 Other 0.06

The bottom cut 'at 87, was withdrawn through line 18 and which con-tained about 50% heavies and 50% alcohol, was discarded.

Overall recovery of propargyl alcohol was 93% 6 The residue `from. the crude distillation column I4 was fed `to the solvent recovery column 19, operated at 40 mm. Hg absolute pressure, where of the N-methyl-Z- pyrrolidone was recovered as distillate at 115 having the following composition:

Component- Percent vN-rnethyl-2-pyr1olidone 95.37 Water 3.79 Propargyl alcohol 0.67 Formaldehyde f 0.17

The residue removed through line 21, and which had the following composition:

Component- Percent Butynediol 46.84 N-methyl-Z-pyrrolidone 50.88 Cuprene 2.28

Component- Percent IButynediol 95.36 Cuprene 4.64

was fed to a cuprene-prec-ipitation tank, where it Was mixed with water at room temperature. The aqueous butynediol-cuprene slurry was [fed to a perforate bowl centrifuge which separated cuprene-rich material from an aqueous butynediol product in the for-rn of a 4clear aqueous solution containing 21.96% of butynediol. Overall butynediol recovery was 93% The process may be carried out with various mixtures of propargyl alcohol and N-alkyl pyrrolidone. Preferably the mixture contains 2 to 30 parts of propargyl alcohol per parts of N-alkyl pyrrolidone. Dilute aqueous mixtures of propargyl alcohol and N-alkyl pyrrolidone containing more than 45%, and preferably more than 35%, by weight, of water may be subjected to a preliminary azeotropic distillation with benzene, cyclohexane, ethyl propyl ether, or isopropyl ether, to reduce the amount ci water in the mixture, if desired.

Propargyl alcohol can be recovered by distillation in accordance with the present invention from admix-tures with various N-alkyl-Z-pyrrolidones having 1 to 8 N-alkyl carbon atoms, that is, derivatives of 2-pyrrolidone in which the hydrogen atom normally linked to the nitrogen atom is substituted by an open-chain saturated hydrocarbon radical having l to 8 carbon atoms in a straight or branched carbon chain.

-It is a -feature of the present invention that the recovery and purification of the propargyl alcohol conta-ined in solution in N-alkyl-Z-pyrrolidone having l to 8 N-alkyl carbon atoms by distillation in accordance with the process of the invention can be carried out in a continuons manner, as shown in FIG. 1 of the drawings, although batch distillation processes can be employed if desired. Another advantage of the present invention is the high degree of separation of components effected by rthe process. Thus, it becomes feasible to combine the separation and purification process of the present invention with the ethynylation process of application Serial No. 847,223, referred to above, and to return the formaldehyde and N -alkyl pyrrolidone, recovered in the recovery and .purification process or the present inventioif to the ethynylation process for reuse in the latter process.

I claim:

1. A process lfor recovering propargyl alcohol yfrom a 7 mixture containing it together with an N-alkyl pyrrolidone having l to 8 N-alkyl carbon atoms, which comprises subjecting said mixture to distillation in the form of an aqueous mixture containing at least 25% iby Weight of water.

2. A process as delned in claim 1 wherein the aqueous mixture contains at least 30% by Weight ofwater.

3. A process as defined in claim 1 wherein the aqueous mixture contains 30%-45% by 'weight of Water.

4. A process `for recovering propalrgyl alcohol from an aqueous solution of propargyl alcohol in N-methyl-Z- pyrrolidone which comprises `adjust-ir'lg the concentration of Water in the solution to at least 25 by weight, distilling the aqueous solution, and collecting a distillate of aqueous propargyl alcohol.

5. A process Ifor recovering propargyl alcohol from an aqueous solution `of propargyl alcohol in N-methyl-2- pyrrolidone containing hutynediol and formaldehyde, which comprises adjusting the concentration of water in the solution to 25%-45% by weight, separating the resulting solution by distillation into an overhead portion containing propargyl alcohol, Water and formaldehyde, 4and a bottoms portion containing N-methyl-Zapyrrolidone butynediol and water, and recovering propargyl alcohol from the overhead portion.

y6. A process as dened in claim 5 wherein lthe concen- 8 tration of water in `the aqueous solution of propargyl alcohol and N-methyl-Lpyrrolidone is adjusted to by Weight.

7. A process of recovering propargyl alcohol from a solu-tionof -propargyl alcohol in N-methyl-Z-pyrrolidone containing kbutyned-iol and formaldehyde, and resulting from the ethynylation of formaldehyde by reaction with acetylene in aqueous Nnnethyl-Z-pyrrolidione as -reaction medium, which comprises Vsubjecting the solution to distillation in the form of an aqueous mixture containing 25%*45% of Water, by weight, separating an over-head distillate containing propargyl alcohol, water and formaldehyde from a bottom cut containing N-methyl-Z-pyrrolidone, butynedol and water, and recovering propargyl alcohol from the 1overhead distillate by distillation.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR RECOVERING PROPARGYL ALCOHOL FROM A MIXTURE CONTAINING IT TOGETHER WITH AN N-ALKYL PYRROLIDONE HAVING 1 TO 8 N-ALKYL CARBON ATOMS, WHICH COMPRISES SUB- 